In the fields of commercial package printing or commercial label printing used for advertising purposes, etc., characters or images have been conventionally printed on a printing medium made of a resin such as PET (polyethylene terephthalate), PVC (polyvinyl chloride), PE (polyethylene), PP (polypropylene) and NY (nylon) using a solvent-based ink, a UV-curing ink, etc. On the other hand, from the viewpoint of reduction in environmental burden, saving of energy, safety, etc., it has been demanded to utilize an ink-jet printing method or a flexo-printing method as a printing method using a water-based ink. In particular, in the ink-jet printing method, droplets of ink are directly projected onto a recording member from very fine nozzles and allowed to adhere to the recording member to form the characters or images thereon. The ink-jet printing method has become rapidly spread because of various advantages such as easiness of full coloration, low cost, capability of using a plain paper as the recording member, non-contact with printed characters or images, etc. In consequence, it has been attempted to utilize the ink-jet printing method for printing the characters or images on the aforementioned resin printing medium.
Patent Literature 1 discloses a white ink for ink-jet printing which contains a white colorant, a first resin constituted of a polyester-based resin, a second resin constituted of at least one of a fluorene-based resin and a styrene-acrylic resin and a third resin constituted of a polyolefin-based wax, and which is capable of recording excellent images that solve at least one of problems including occurrence of cracks, deterioration in abrasion resistance and deterioration in adhesion properties.
Patent Literature 2 discloses an image printing method including an ink applying step of applying an ink composition that contains a colorant, polymer particles A containing a polyolefin component which are subjected to a modification treatment selected from chlorinating modification, acrylic modification and maleic anhydride modification, and polymer particles B having a structural moiety that is different from that of the polymer particles A, onto a recording base material in the form of an aggregate of non-ink absorbing or low-ink absorbing fibrous materials by an ink-jetting method. In the Patent Literature 2, it is also described that the images obtained by the image printing method are excellent in adhesion between the ink composition and the aggregate of non-ink absorbing or low-ink absorbing fibrous materials (nonwoven fabric formed of resin fibers, etc.) and rub fastness.